Re: [PATCH] slub: avoid scanning all partial slabs in get_slabinfo()

[Christoph Lameter (Ampere)]

On Wed, 13 Mar 2024, Jianfeng Wang wrote:

> I am not sure that the RCU change will solve the lockup problem.
> The reason is that iterating a super long list of partial slabs is a problem by itself, e.g., on a
> non-preemptive kernel, then count_partial() can be stuck in the loop for a while, which can cause problems.
>
> Also, even if we check the list ownership for slabs, we may spend too much time in the loop if no updater shows up,
> or fail and re-do many times the loop if several updates happen. The latter can exacerbate this lockup issue. So,
> in the end, reading /proc/slabinfo can take a super long time just for a counter that may be changing all the time.

Well we could also cache the values somehow to avoid the scans? invalidate 
the counter if something significant happens.


> Thus, I prefer the "guesstimate" approach, even if the number is inaccurate or biased. Let me know if this makes sense.

Come up with a patch and then lets see how well it works.